- Chair upholstery material any damage resulting of: - Strong blow on transportation- Repair or dismantling of product by any person other than Arvand qualified service personnel- Continuous usage of material on uneven surfaces- Uneligible or tampered product number on guarantee certificate sales invoice or product body- Product guarantee number not matching that on product- When purchase date can not be verified i.e due to loss of purchase invoice, date of manufacture shall be used as start of guarantee.